There's plenty of teams around the league dressing worse defeseman on a regular basis because of size and all that. The big lumbering third pairing defenseman trope still exists even though it really shouldn't. Just dress a guy you can play for 10-15 minutes that doesn't f*** up and can handle the puck a bit. At this point i don't think you can play without mobile defenseman on any pairing anymore outside of some grizzled vets like Sekera who have enough experience that they can compensate with positioning.
There really aren't. And the ones that did, and had skill elsewhere on their team, did pretty well. The Stars were the tallest team in the league this past season so if anyone overvalues size it would be them. But Tampa ran Schenn and Bogosian all the way to a Stanley Cup Final until Rutta came back.
When you say "just get a guy that doesn't f*** up", like, that's not so easy. And I think it's easy to take it for granted as a fan of an elite defensive team. But that's part of what separates the mediocre teams from the elite teams. A 3rd pairing that can actually go out there and not get victimized. It's not as though when Chicago trots out Adam Boqvist and Slater Koekkoek or when Toronto trots out Travis Dermott and Justin Holl, or Caleb Jones and Matt Benning for Edmonton, or Jack Johnson and Justin Schultz in Pittsburgh, the list goes on. It's not as if those teams ran with "big lumbering third pairing" defensive defensemen. Take Jonas Seigenthaler on Washington for example. He was absolutely lit up in the playoffs. Great skater...the rest not so much.
The commonality with all these under-performing teams isn't a preference for hulking-stay-at-home defensemen. I think the teams that made it far into the playoffs had a lot of success signing veteran stay-at-home defensemen with a lot of experience to their third-pairings. The one outlier is Zach Whitecloud, who was arguably the best defensive defenseman in the playoffs, was a UFA discovery. But it does seem that these veteran blue-liners bring a lot to the table so long as they can keep things tidy in their own end.